1. Field of the Invention
The present invention relates to a video recording apparatus and method, and a video output apparatus and method, in which television signals based on a predetermined standard such as NTSC or the like are supplied, and the supplied TV signals are digitally encoded for recording to a recording medium such as a DVD (digital versatile disk).
This application claims the priority of the Japanese Patent Application No. 2003-107053 filed on Apr. 10, 2003, the entirety of which is incorporated by reference herein.
2. Description of the Related Art
As a device for recording TV broadcast programs or photographed images, DVD recorders each using a recording DVD as a recording medium have become popular, taking the place of the conventional video tape recorders. The recording DVD is an optical disk of 12 cm in diameter and 1.2 mm in thickness and has a recording capacity of 4.7 giga-bytes.
There have been proposed recording DVDs of five formats including DVD-R, DVD-RW, DVD+RW, DVD+R and DVD-RAM. “R” stands for “recordable (“write once, read many)” and “RW” stands for “rewritable (rewritable more than once)”. These formats were proposed by the consumer specification association “DVD Forum” (Internet address: URL:http://www.dvdforum.gr.jp/) and another consumer specification association “DVD+RW Alliance” (Internet address: URL:http://www.dvdrw.com/).
Also, the above DVD specifications adopt the MPEG-2 technique for video and audio encoding. A DVD recorder encodes input video and audio signals by compression with the MPEG-2 technique to create an MPEG-2 data stream, and makes authoring of the MPEG-2-based data stream for recording to a DVD.
Also, for recording NTSC-based TV signals by the DVD recorder, an asynchronous system is applied not to synchronize the vertical sync timing (V timing) of an input signal with the V timing of the MPEG-2 data to be recorded in some cases.
In the above asynchronous system, in case the V timing of the signal to be recorded is shorter in cycle than that of the input video signal (namely, the recording clock is earlier), an underflow that “a frame not yet supplied has to be outputted” takes place at a time. At this time, a shift between the V timing of the input video signal and that of the signal to be recorded is adjusted by outputting a precedent frame repeatedly as the case may be. Such an adjustment is called “frame repeat”.
On the contrary, in case the V timing of the signal to be recorded is longer in cycle than that of the input video signal (namely, the recording clock is later), an overflow that “a preceding frame is not yet outputted but a next frame is inputted” takes place at a time. At this time, a shift between the V timing of the input video signal and that of the signal to be recorded is adjusted. This adjustment is called “frame skip”.
The TV signal broadcasting methods include a “video multiplexing telecasting” or “teletext” in which a closed caption, text information, data for controlling the closed caption and text information, etc. are inserted in a predetermined horizontal scan period within a vertical blanking time (on a twenty-first horizontal line, for example). Information for insertion into the horizontal scan period within the vertical blanking time is generally called “vertical blanking information (VBI)”. In the video multiplex telecasting or teletext, VBI is transmitted over a succession of frames and the frames as a whole defines the VBI.
When recording a TV signal including such VBI, the DVD recorder detects the VBI while the VBI is still a NTSC-based or PAL-based TV signal, and encodes the detected VBI into a header of each GOP of an MPEG-2 data stream.
Note here that in case the aforementioned frame repeat or frame skip has occurred, the VBI inserted in a blanking time, for example, will also be repeated similarly to the frames or arbitrary data thereof have deleted. Thus, the VBI will lose continuity, for example, character data will be garbled and become meaningless.